951pcarguy

No spark from my 87 951 with Lindsey MAF, even after replacing the Coil, Wires, Cap, and Rotor, and verified I have 12V to the MAF unit. What else could it be?

The problem started as intermittent cutting out, and quitting when wet, then hard to start, now no fire at all. Plenty of fuel, as I can smell it if I crank it for a while.

Help!

Jay Ellis
'87 951 Apline White
'87 951 Guards Red (deceased)

travisgreen

I've had nothing but problems with a recent lindsey maf, still waiting for a replacement after over a week of being on " back order ". But it doesn't sound like it has anything to do with that. Check your crank sensor harnesses behind your intake manifold by the firewall. Jiggle them and make sure they are connected properly.

Black51

Getting tach bounce?

refresh951

Check the speed and ref sensors. Very common for the wiring/connectors to the sensors to have issues. If they are not functioning properly it results in a "no fire" condition in the DME and thus no spark.

951pcarguy

Barely any bounce on the tach when trying to start, but it does move slightly.

Where are the speed, ref, and crank sensors and what do they look like? Sorry for the rookie questions.

Jay

refresh951

No worries. Look here:

http://www.clarks-garage.com/shop-manual/ign-02.htm

travisgreen

They are all the same thing. The harnesses go bad more often than the actual senors. Directly behind your intake manifold back by the firewall. Unless someone removed it at some point the plug clips will be in a bracket. There are 2'

travisgreen

Good info although you may want to check resistance at the dme harness under the passenger seat instead . that way you don't get a false reading if your sensors are good but your harness is bad

951pcarguy

So do I need an Oscilloscope to check DME resistance (as the how-to from Clark's suggests) or can I verify it's working OK with just a multimeter?

Jay

bw993

Are you running the Quad MAF from Lindsey? If so, it probably is the MAF. I had two of those things die on me the same way.

travisgreen

Are u serious? I love how everyone there and at abaco tell me it's probably not the MAF they never have issues with them.
Back to the no spark issue though, a faulty maf won't cause a no spark

travisgreen

Can be done with a multimeter, just make sure it's set to ohms and is capable of reading at least 1600

951pcarguy

I do have the Quad MAF so what part normally fails, and does Lindsey replace it under warranty?

travisgreen

Your maf is not the reason you don't have spark, I'd figure that out before trying to send other parts back

bw993

The issue with the QUAD MAF is that it has digital electronics (i.e. micro-controller) mounted with the MAF sensors, just behind the air filter. This orientation exposes the digital electronics to the elements (i.e. moisture). The two that I had were not well sealed and the PCBA for the unit easily collected moisture and condensation. Moisture and digital electronics do not mix. This is especially an issue with where the MAF pipe is positioned in 951. For my issues, I had an oscilloscope and confirmed it. Keep in mind that when the micro-controller of the QUAD MAF fails, this is not the same has just a bad MAF element for an analog MAF. When the digital electronics/micro fail, the DME does not see any voltage level from the MAF via the AFM connector, which results in DME not providing drive current to the negative terminal of the coil (i.e. no ignition). Hopefully, your issue is not the same.

Sorry for being so verbose, it's just the EE in me.